Process of vulcanizing rubber to leather



Patented July 8, 1930 UNITED STATES PATENT OFFICE LEON IB. CON-ANT, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOB, BY MESNE ASSIGN- MENTS, TO STANDARD SAOHUSETTS PATENT PROCESS CORPORATION, A CORPORATION OF MAS- PROOESS OF VULOANIZING RUBBER TO LEATHER llo Drawing.

' process of vulcanizing rubber to leather, an

essential step in which is a pro-heating of 6 the leather at a temperature substantially equal to that of vulcanization; and in m companion application filed October 4, 1926, Serial No. 139,345, I set forth an improvement upon the previous process consisting in dehydrating the leather at a moderate temperature prior to its pie-heating.

These are most important improvements 1n the art because the pro-heating of the leather at a temperature substantially equal to that employed in the subsequent vulcanization of the rubber composition thereto, assures its successful adaptation to the heat of its union therewith, which commonly exceeds 300 F.,

v and if prior to its pre-heating, care is taken t0 dehydrate the leather at a moderate temperature, preferably at less than 200 F., the very great advantage is secured of working a uniform material during its subjection to the pre-heating operation and following introduction in company with the rubber to the heat of vulcanization. Accordingly, since this process is designed to accommodate all manner and kindsp'f leathers, for successful combination with rubber composition by hot vulcanization, it is necessary to dehydrate at moderate temperature, and thereby to assure the uniformity of condition of the leather from then on, as it works its way through the process, this feature cannot be emphasized too strongly. This manner of dehydrating is extremely advantageous because it guarantees in combination with the pre-heating operation the retention by the leather fibres of that prime condition or circumstance that later permits as this process will describe, the full eventual restoration of fibre-toughness and therefore of serviceability to the leather.

his process, therefore, has as its objective the preservation of the original qualities in the leather throughout the several different steps of its manipulation or handling prior to, during and following its combination with the rubber, and, it 1s the applica-v tion of these several steps in combination, and

Application filed November 1, 1926. Serial No. 145,489.

in the natural sequence described, that together constitute the guarantee that the leather shall regain all of its attributes or qualities as originally possessed.

There is also another hazard in working leather successfully that dehydration at a temperature of 200 F. or less overcomes, and

that is the condition commonly found wherein pieces of leather are pasted or glued together, thereby permitting the utilization of scrap or ofi'al leather that, because of such assembly has become of greatly enhanced value and acceptability in many lines of manufacture, and particularly in shoe making.

If, therefore, such pasted or glued leather is to be adapted to successful combination with rubber composition by hot vulcanization, even the most casual consideration enforces the realization that any medium, as glue, clogging the pores of the leather offal to be prepared for processing, is a handicap that, if not recognized and controlled, would become a serious impediment, since,'lying within the leather body, it is in effect a veneer or coating quite likely to function as a very effectual blockade to the enforced movement of the normal moisture content of the leather "upon its subjection to a temperature approaching thatcommonly employed in vulcanization, and, if disregarded, this coating or' veneer will surely 'become the agent of destruction ruining the vulcanized combination.

Accordingly, and as recited above, the act of dehydration at a temperature less than 200 F. provides, because of the complete or partial presence or utilization of' pasted or glued leather offal, that degree of accommodation requisite to adapt the leather offal to this process prior to its pro-heating at a much higher temperature, since the comparatively low temperature of such dehydration slowly but surely removes the normal atmospheric content of moisture in the leather entirely without injury to the leather fibres, and without disturbing the union between the pasted or glued parts, as the slowness of the drying-out creates no radical disturbance of the fibrous relationship or cohesion as promoted by the paste or glue.

When, now, the leather has first been dehydrated at a temperature of 200 F. or less, and then pre-heated at a temperature substantially equal to that employed in ts later combination with the rubber composition by hot vulcanization preferably with pressure, at ordinarily a teinperaturein excess of 300 F., and following such pre-heating has been vulcanized as described, there is now at hand the fruit of successful processing, the vulcanized combination leather and rubber article, but lacking withal such a degree of naturalness in so far as the leather is concerned, that the futility of further prohibition em phasizes and commends the value inherent in prompt and adequate restoration to normalcy.

Accordingly, the next step in this process is that of providing the leather with an abundance of moisture; and-such moisture content being enforced, may be obtained either by means of a properly humidified atmosphere, or preferably by immersion in water. Having, therefore, soaked the leather in a water bath, which it absorbs with the appetite of a glutton, its fibres drink their fill and it becomes unserviceable; but by giving it a partial dehydration in a suitable atmosphere, the super-content of moisture is removed and thevulcanized article of leather and rubber is now perfectly ready for service.

; The process may therefore be summarized as comprising the acts of dehydration at moderate temperature; pre-heating at vulcanizing temperature; bringing the leather while superheated into company with the rubber composition and vulcanizing the latter thereto; then restoring a normal moisture content by enforcing a super-abundance thereof, and then reducin the same by evaporilfation in a partially dehydrating atmosp ere.

Where the articles thus produced are combination heels, they can be at once attached to footwear and properly trimmed to fit the same, without the swelling and consequent" mis-fit which otherwise occurs, where there is no hydrating following vulcanization.

What I claim as my invention is: 1. The process of vulcanizing rubber to leather,

j ectin'g the leather to a temperature substantially equal to that of vulcanization; uniting and vulcanizing the rubber thereto; immersing the leather in water; and finally drying it to retain a normal amount of moisture. v

4. The process of vulcanizing rubber to leather, consisting infirst dehydrating the leather at a moderate temperature; then subjecting it to a temperature substantially equal to that of vulcanization; and then uniting and vulcanizing the rubber thereto with heat and pressure.

5. The rocess'of vulcanizing rubber to leather which consists in dehydrating the leather at a moderate temperature, then preheating the dehydrated leather at an elevated temperature thereby energizing the leather with a super-heat, and then while so energized withheat bringing it in company with rubber into the heat of vulcanization and uniting and v'ulcanizing the rubber thereto; and finally re-hydrating the leather by introducing the vulcanized combination water for asuitable time.

In testimony that I claim the fore oing invention, I have hereunto set my ban this 29th day of October, 1926.

LEON B. CONANT.

consisting in first dehydrating the leather at a moderate temperature; then sub- 1 ectmg the leather to a temperature substan- 1 tially equal to that of vulcanization; and then un tn ig1 and vulcanizing the rubber thereto.

2. e process of vulcanizing rubber to leather,

consisting in first dehydrating the leather at a moderate temperature; then sub- Jectmg the leather to a temperature substantially equal to that of vulcamzation; and then uniting and hot vulcanizing the rubber thereto.

3. The process of vulcanizing rubber to leather, consisting in first dehydrating the leather at a moderate temperature; then sub- 

